The present invention relates generally to a DC distribution module or assembly for mounting a plurality of overcurrent protection devices, such as plug-in circuit breakers, fuse modules and fuse blocks. More particularly, the present invention is directed to the combination of one or more fuse blocks mounted on an assembly including one or more busbar modules on which said plurality of plug-in circuit breakers or fuse modules are also mounted, wherein the busbar modules contain female receptacles for receiving male plugs disposed on the fuse blocks, along with female receptacles for receiving auxiliary alarm contact terminals on the fuse blocks.
There are numerous electrical system applications which require the use of a plurality of overcurrent protection devices, such as circuit breakers or fuse modules, to shut off current in one or more portions of the electrical system in response to an overcurrent condition. Fuses typically have a conductive wire element that rapidly heats and melts in response to an overcurrent condition, forming an open circuit. Fuses are often packaged in fuse modules containing additional circuit elements which transmit an alarm signal if the fuse opens in response to an overcurrent condition. Circuit breakers commonly comprise a movable electrical breaker contact and a stationary breaker contact. The movable electrical contact is typically coupled to an actuator mechanism that utilizes an electromagnetic device to open the breaker contacts when an over-current condition is detected. During normal circuit operation, the actuator mechanism electrically couples the breaker contacts so that the circuit breaker is in a conducting, or on-state. However, when an over-current condition is detected, the circuit breaker trips, and enters a non-conducting, or off-state. A handle on the external surface of the circuit breaker is commonly coupled to the actuator mechanism. The actuator-handle provides a visual indication of the state of the circuit breaker (e.g, on, tripped, and off) while also permitting the user to reset the circuit breaker after the circuit breaker has been tripped or to deliberately turn the circuit breaker off during routine repair or maintenance. Some circuit breakers include an additional alarm circuit, which sends an alarm signal to other circuits when the alarm circuit senses that the circuit breaker has been tripped.
FIG. 1 shows a perspective view of a prior art circuit breaker module 100 used in a power distribution module. A plurality of circuit breakers 110, 120, 130 are coupled by frictional forces or by mechanical connectors to base 180 and front face plate 122. Each circuit breaker 110, 120, 130 has a corresponding actuator handle 105. As shown in FIG. 1, screw connectors 131 are commonly used to electrically couple circuit breakers 110, 120, 130 to busbars 162, 164 and connectors 160, 161, 151 to couple current to a rear connector 134 on panel 124. Bus bars 162, 164 couple a negative polarity power terminal, often called a line terminal, of each circuit breaker 110, 120, 130 to a negative power terminal. Connectors 160, 161, 151 separately couple the load terminal, often called the positive power terminal, of each circuit breaker 110, 120, 130 to separate electronic loads.
While circuit breaker module 100 provides the benefit of several circuit breakers 110, 120, 130 arranged to control the current or power in different portions of a power distribution module, it has several drawbacks. One drawback is that it may be inconvenient to replace one of the circuit breakers 110, 120, 130. Replacement of circuit breakers may be required if a circuit breaker is damaged. Additionally, circuit breakers may need to be replaced if it is determined that a different response is required by the circuit breaker. For example, the user may determine that a higher amperage circuit breaker is required for a particular application. The time to replace a circuit breaker 110, 120, 130 in module 100 may be significant because the total time to replace a circuit breaker includes the time to: 1) withdraw the module; 2) remove any exterior housing elements surrounding the screw connectors 131; 3) disconnect the screw connectors 131; 4) extract the old circuit breaker; 5) insert a new circuit breaker; 6) connect screw connectors 131 to the new circuit breaker; 7) attach any exterior housing elements; and 8) re-insert module 100.
Another drawback with circuit breaker module 100 is that the housing and connector are comparatively bulky. There is a general trend to miniaturize all aspects of power supply and power distribution systems. Unfortunately, the total volume of circuit breaker module 100, including connectors 131; busbars 162, 164; and connectors 160, 161, 151 is significant.
Still another drawback with module 100 is that it does not address the problem of circuit breakers with alarm circuits. Circuit breakers with alarm circuits typically have additional auxiliary terminals for sending an alarm signal that is indicative of the operating state of the circuit breaker. For example, an alarm circuit preferably sends a logical xe2x80x9chighxe2x80x9d signal from an alarm terminal to indicate that the circuit breaker has been tripped due to an overcurrent event. The alarm signal may, for example, be used to trigger an indicator light to alert the user that a circuit breaker has been tripped. Circuit breakers have two alarm contact terminals. More commonly, however, circuit breakers have three alarm contact terminals corresponding to normal-off, normal-closed, and common terminals. An electrical connection must be provided to each alarm contact terminal of each circuit breaker of a circuit breaker module. Unfortunately, this increases the complexity of the electrical connection required in a circuit breaker module.
FIG. 2 is a prior art side-view drawing of a circuit breaker 210 with an alarm circuit 220 providing an alarm signal via stab-type alarm terminal 216. Line contact 212 and load contact 214 also comprise stab-type connectors. Stab-type connectors are a type of connector that has a comparatively thin, blade-like connector surface which is pressed into a female connector slot or socket (i.e., xe2x80x9cstabbedxe2x80x9d) to form a tight mechanical and electrical coupling. Stab-type connectors have the advantage that the small surface area of a male stab-type connector permits a significant penetration pressure to be applied in inserting the male connector. However, stab-type connectors have the disadvantage of having a comparatively small cross-sectional area for current to flow.
FIG. 3A is a perspective view of a prior art circuit breaker module 254 designed to be loaded with a plurality of circuit breakers 210 having stab-type line and load terminal connectors 212, 214 (not shown) and stab-type alarm contact terminal connectors 216 (not shown) as illustrated on the circuit breaker 210 of FIG. 2. For the purposes of illustration, three circuit breakers 210 are shown installed in a module 254 designed to hold a total of four circuit breakers. A busbar 288 is used to provide an electrical connection to line contacts 212. Contacts 256 are spring-biased receptacles configured to contact load contacts 214. Additional connector legs 282 facilitate installation of module 254 as an integral unit.
FIG. 3B is a top view of module 254 with circuit breaker 210 removed, to more clearly show the electrical connectors. Each aperture 260 allows passage of a line contact 212 (not shown) in order to receive power from a power source. Spring biased alarm contacts 262 are dimensioned to mate with corresponding alarm terminals 216 (not shown) for respective circuit breakers 210. The alarm contacts 262 are electrically connected to each other by alarm contact line 264. Load connectors 258 provide a bolt and screw connection site to secure external electrical lines.
While circuit breaker module 254 provides several benefits, it has several drawbacks. One drawback of stab-type connectors is that they have a limited structural strength, i.e., the comparatively small cross-sectional area of each stab-type terminal 212, 214 provides only limited resistance to transverse and rotational forces. However, if circuit breaker 210 is mounted to a socket perpendicular to a vertical surface, the force of gravity will generate transverse and rotational forces acting to dislodge the stab-type connectors. This may necessitate the use of long stab-connectors with a high contact pressure, which increases the difficulty of inserting or removing a circuit breaker. In some cases, additional support structures, such as a frame and screw connectors, are required to maintain a circuit breaker with stab-type connectors within their sockets. Another drawback with circuit breaker connector module 254 is that it does not address the need for reducing the cost per electrical connection. The cost of circuit breakers, like other electronic components, continues to decrease over time. It is desirable that the cost of the connector module divided by the number of circuit breakers decreases as the connector module is increased in size to accommodate a larger number of circuit breakers. This is commonly known as xe2x80x9cincreasing returns to scale.xe2x80x9d Stab connector receptacles 256, 262 will tend to have a substantially constant price per female receptacle, assuming that they are purchased from a commercial vendor in large production lots. However, as can be seen in FIGS. 3A and 3B, circuit breaker module 254 requires a substantial support structure including connector legs 282 and support surfaces 284 to facilitate removing or installing module 254 as an assembled unit into an electrical system. The material cost of the support structure will tend to increase as the module 254 is increased in size to connect additional circuit breakers. Consequently, it can be expected that there will be no significant cost reduction to increasing the size of module 254 to accommodate additional circuit breakers.
The need for a compact, low-cost circuit breaker connector module is especially important in the context of plug-in circuit breakers. As shown in FIG. 4, compact plug-in circuit breakers 400 commonly have power connections comprised of male plug-shaped connectors 410. Additionally, plug-in circuit breakers commonly include additional alarm contact terminal connectors 420 for transmitting an alarm signal. Typically there are three alarm contact terminals 420 corresponding to a common terminal, a tripped signal terminal, and an off-terminal. The alarm contact terminals may be any style of male plug, but are typically in the form of pins, prongs, or blades with planar surfaces.
It is desirable in many applications, such as telecommunication applications, to utilize a large number (e.g., ten to twenty) of plug-in circuit breakers 400 as part of a power distribution system. Unfortunately, there is no commercially available connector module that provides electrical connections to both the male plugs 410 and alarm contact terminals 420 of a single plug-in circuit breaker 400. Typically, separate wire connections are soldered to each of the alarm contact terminals 420 after the male plugs are plugged into two female socket receptacles.
Part of the problem of designing a connector module for a plug-in circuit breaker 400 is the different requirements of male plugs 410 and alarm contact terminals 420. The male plugs 410 of plug-in circuit breaker 400 preferably fit into female sockets (not shown in FIG. 4) with a friction fit so that the male plugs may be inserted or withdrawn in order to insert or remove the circuit breaker. In the context of circuit breakers without alarm contact terminals, this permits what is commonly known as xe2x80x9cplug and playxe2x80x9d operation, since both mechanical and electrical connection to the circuit breaker is made by inserting the plugs 410 into their sockets. However, the compact male alarm contact terminals 420 also require a reliable electrical connection in order to provide reliable alarm signals. Unfortunately, the differences in size, shape, and length of planar alarm contacts 420 compared with male plugs 410 make it difficult to design a low-cost connector socket that simultaneously mates with an appropriate friction fit to both types of male plugs 410 and auxiliary contact terminals 420.
The two different styles of male terminal connectors 410, 420 makes it difficult to achieve a friction fit with the appropriate connection length and pressure for both types of male connectors 410, 420 in a low-cost structure with reasonable fabrication tolerances. This problem is exacerbated in the context of circuit breaker modules in which the circuit breakers are mounted with the axis of the male connectors disposed perpendicular to the force of gravity, i.e., with the force of gravity acting to torque the male connectors. One potential solution to this problem is to use additional clamps or screws to apply a pressure between the male connectors and sockets. Clamps and screws are commonly used in some types of electrical connectors to facilitate the mating of different types of male connectors to a common female connector. However, additional clamps or screws increase the cost of the connector and also require the user to spend additional time to adjust the clamp or screws in order to remove or install the male connector. Moreover, clamps and screws are inconsistent with xe2x80x9cplug and playxe2x80x9d operation.
As none of the conventional approaches meet these needs in a fully satisfactory manner, what is desired is a distribution assembly for accommodating a plurality of overcurrent protection devices in which all of the male connectors of each overcurrent protection devices are demountable with the female sockets of the assembly by friction coupling. There is a need to expand the connector module in an easy and convenient manner to enable a large number of plug-in circuit breakers and fuse modules to be accommodated as a part of a power distribution system for telecommunications applications. No known prior art connector module design possesses all of the desired characteristics in a modular distribution assembly.
It is also clear that increasing the number of fuses mounted on an assembly allows a greater number of circuits to be protected. Often though, the space constraint of the particular telecommunication application permits only a limited number of plug-in circuit breakers and connector modules to be used. Thus, there is a need for another manner of expanding upon the number of fuse positions in a group of connector modules. In this situation, it would be highly desirable to accommodate a maximal number of fuses for these large scale telecommunication applications but in a compact manner.
The present invention is directed towards a connector module comprising a DC modular distribution assembly for providing what is called xe2x80x9cplug and playxe2x80x9d electrical connections to a plurality of overcurrent protection devices. The overcurrent protection devices each have first and second male electrical plugs, and electrical connections to each overcurrent protection device are automatically made by inserting the overcurrent protection device into corresponding female sockets in the assembly. One or more fuse blocks containing a plurality of fuse positions may also be inserted in the assembly in place of one of said overcurrent protection devices.
The first embodiment of the connector module of the present invention is directed towards providing plug and play electrical connections to a plurality of circuit breakers, wherein each circuit breaker has both male plugs and auxiliary signal terminals. In the first embodiment, the mounting substrate is a printed circuit board and further comprises auxiliary signal terminal passageways and clips mounted to the second side of the substrate to provide an electrical connection to the auxiliary signal terminals.
One object of the present invention is a low-cost connector module adapted for plug-in circuit breakers with crown-style male plugs. In the first embodiment, the sockets comprise protruded holes dimensioned to mate with the crown-style male plugs.
Another object of the present invention is a low cost clip connector for making contact to auxiliary signal terminals. Each clip is sized, shaped, and positioned to grasp a single auxiliary terminal whereas electrical connections to each clip are made by tracks on the substrate.
Still another object of the present invention is a low cost manufacturing method to fabricate the connector module.
In a preferred embodiment of the present invention, a DC modular distribution assembly is provided with one or more busbar modules for mechanically mounting and providing electrical connections to a corresponding number of overcurrent protection devices each having first and second male electrical plugs. Each assembly comprises a first support member having a mounting substrate with a first side and a second opposed side. The support member includes a plurality of first plug passageways disposed adjacent the mounting substrate. At least one conductive line busbar member is mounted to the support member and includes at least one first socket shaped and positioned to mate by a friction fit with a corresponding first male plug extending through a corresponding one of the first plug passageways. The support member also has at least one load busbar module installed thereon. Each load busbar module includes a conductive load busbar member and a second plug passageway, wherein the plug passageway is shaped to permit passage of a second electrical plug of each overcurrent protection device in a direction from a first side to a second side. Each conductive load busbar member includes a second socket shaped and positioned to mate by a friction fit with the second male plug extending through the second plug passageway. The support member and load busbar module are non-conductive so that the first male plugs of each overcurrent protection device and corresponding line busbar members are electrically insulated from the second male plugs and from each load busbar member.
One important technical advantage of the preferred embodiment is that it permits one to install only as many load busbar modules as needed for the particular system. Another advantage is that with such a modular design, an assembly of busbar modules, for accommodating a plurality of plug-in circuit breakers, may be readily assembled very quickly and easily, without the need for additional tools or hardware. The use of snap-in load busbar modules also avoids having to include the entire complement of busbars with each assembly.
In a preferred embodiment of the present invention, the overprotection device comprises a ten-position plug-in fuse block in addition to the plug-in circuit breakers and fuse modules already discussed. The ten-position plug-in fuse block occupies the space required by overcurrent protection modules. When the ten-position plug-in fuse block is coupled to the distribution assembly of the present invention, a greater number of fuses is made available to the system. Not only does this embodiment increase the number of fuses and thereby permit a larger number of circuits to be protected, but does so while maintaining the flexibility offered by the assembly according to the present invention. In other words, each fuse block includes two guide pins and preferably a latch, which make use of snap-in busbar modules for mounting of the fuse block on the distribution assembly, thereby avoiding having to pre-manufacture the support member with an entire complement of busbars. With such a modular design, an assembly of plug-in circuit breakers, fuse modules and fuse blocks may be readily assembled very quickly and easily, without the need for additional hardware.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description and from the detailed drawings.